Amplifiers are employed in a wide variety of settings in electronics. Many such circuits have current regulation. Some applications for these circuits draw excessive current during power on, which can cause system components to burn up due to improper powering of supplies. Other applications may need to limit the current provided by an operational amplifier (also called an “op amp”) to a load, or due to other considerations. For example, amplifiers with applications in testing equipment, industrial printing, and general high voltage or current applications, among others, may require current limiting to avoid operational breakdown or other failures of the amplifiers.
Current limiting circuits, such as those dependent on base-emitter voltages of bipolar junction transistors or those dependent on other component process characteristics or parameters, can be susceptible to performance variation and inaccuracies as temperature or process characteristics or parameters change. Base-emitter, or Vbe-based schemes typically divide an approximate diode voltage by the desired current to determine the size of a current-limiting resistor to achieve desired current limitation. Such Vbe-based schemes may vary widely over process, and may have a negative temperature coefficient (TC) of approximately 2 mV per degree Celsius, meaning the current limit is not substantially constant over temperature or process. Other current limiting circuits, such as those scaled to an output device current that is used for detection, may not be feasible under design or other constraints, and may waste power or other resources. Some current limiting circuits may also depend on varying parameters and may not allow for selectable current limits.